Fouling of cooling surfaces of industrial crystallizers is a major problem which reduces the productivity of installations. This phenomenon, which results from the surface temperature being lower than that of the bulk so as to allow heat transfer, is essentially initiated by primary heterogeneous nucleation. The experimental setup has been designed to study the influence of different parameters such as suspension flow velocity, temperatures, the nature and the finish of the deposit surface, as well as the nature of the product which crystallizes. The conditions of the appearance of a crystalline layer and its subsequent growth are studied simultaneously by measuring the inlet and outlet temperatures of the two fluids which leads to calculation of the degradation of overall heat transfer coefficient and, more directly, by physically measuring the evolution in time of the thickness profile.